Many accidents or ailments can result in a person losing function in a body part. For example, nearly 800,000 individuals in the United States experience a new or recurring stroke every year, and the resulting hemiparesis can impair the motor function of a stroke survivor. There are also approximately 12,000 incidences of Spinal Cord Injury (SCI) in the United States each year. In moderate to severe cases, a person may undergo physical therapy in order to restore function to the impaired body part.
Physical therapy is the typical rehabilitation procedure for a person who loses function in a body part, including people who survive a stroke or a spinal cord injury. Some types of physical therapy require one-on-one physical interaction between a therapist and the injured person. While effective in many instances, these types of physical therapy can have several limitations. Due to human nature, different physical therapists may have different techniques, different systems or programs, and different levels of proficiency that result in a wide variety of outcomes for the injured person. In addition, a physical therapist may have difficulty in objectively evaluating the performance of an injured person with quantitative metrics such as the force generated by the injured person's body part or the precise movement trajectory or range of motion of the person's body part expressed in angles, distance, and other similar metrics. A physical therapist may also have difficulty in precise and repeatable application of forces, torques or trajectories to the person's body part.
Some attempts have been made to incorporate machines or robots into the physical therapy process to address some of the deficiencies outlined above. Some examples may be found in U.S. Patent Publication Nos. 2010/0280628, 2008/0009771, 2012/0330198, 2007/0225620, and 2011/0313331, which are incorporated herein in their entireties by reference. In another example, a wrist and upper extremity motion system is described in U.S. Pat. No. 7,618,381 (“the '381 patent”), which is incorporated herein in its entirety by reference. The '381 patent describes a system that secures a person's forearm and permits movement of the person's arm and hand in multiple degrees of freedom. However, the design described in the '381 patent relies on multiple motors interconnected to differential motors and gear systems. This configuration physically limits the range of motion of the person's arm, wrist, and hand in some directions and allows backlash which can deteriorate fidelity of force feedback. The '381 patent presents an “open on top” design, which requires use of limited number of bearings/guides that cannot provide support across a complete rotation. This configuration requires use of bulkier or heavier materials and parts to ensure device rigidity or structural integrity.
These deficiencies, among others, are addressed in the present invention described in detailed below.